Hi Ellen I also grow some plants in water but I never put any fertilizers in the water I just change it often. When I pot up the plant from the water to soil the plant always looks a little sad because it's loosing it's water roots and has to start producing roots for soil. I give them a rest from bright light until I see new leaves growing then put it back in the light. I'm sure some one with more experience can explain it better but that's how I do it.

Regarding the mint:
Keep in mind that when you planted the mint in the soil the mint lost a lot of its roots -- and definitely all the roothairs (which are responsible for water and nutrient uptake). Water roots and soil roots are not the same in structure. Once the mint gets past the initial shock of the root loss and has grown soil roots, it should do very well.

Rosemary:
A very difficult plant for most folks to keep alive let alone happy indoors. Some do succeed, however, so hopefully you will be one of those lucky ones. You could indeed experiment with adding a drop or two of liquid fertilizer now and then.

If the container the plant is in is clear, then algae will show up at some point. While many people assume that's a bad thing (or simply don't like the looks of it) I have known people who found that their plants did not seem to suffer at all from the presence of algae. They found some plants even seemed to perform better. But if algae is not for you and you wish to continue trying to grow the rosemary in water then consider:
1) using an opaque container (will deprive algae from receiving light necessary for photosynthesis);
2) performing regular (2X/week or more) complete water changes;
3) and regularly thoroughly scrubbing out the container you are using.

You might also consider trying semi-hydroponics. (You can find out more about that by either Googling, or popping over to the Hydroponics Forum and doing a search for "semi-hydroponics" or "semi-hydro".)

oh, I need that icon that shows slapping the forehead: duh! :)
Now I do remember what you both said about planting in soil vs water. I had known that, but forgot. So I may try the mint again.
But as far as the Rosemary, I know it is very difficult to grow it inside, and I have forced hot air for heat.
so I'm just going to keep it in water for as long as it lasts.

it's all gravy, since I did not think i'd have it more than few days.
Plus yesterday I bought some thyme and sage (potted) from the supermarket. I am all out of room and still buying! Kinda like when I garden outdoors. :)
but as a first time indoor gardener I am enjoying it. Just ordered some grow lights.
I change the water almost every day.
I'll check out semi-hydro. thanks. did not know about that.

thanks to both of you for your feed-back. This is a great forum.
I am learning a lot.

hi
Would think RM would do well in a dry house?? They come from the Meditettanen clime . I can't keep them due to the humidity . gary

I have never had success growing rosemary. The first rosemary plant, was my mothers and she let my sisters take care of it. They did not water it. That one was not under my care and so I guess not my fault.

A few years later I got another rosemary plant. It was thriving out side, in a pot, on the side of a grill. One day my mother turned on the grill and noticed that something smelled like burning rosemary. Oops! That plant died but I was able to save the basil that was also burnt at that time.

Good luck with your rosemary. From what I can tell It is not a particularly picky plant, but I don't have much experience.

In conclusion:
Do not burn rosemary plants.
L.G.